Method of and apparatus for depalletizing commodities

ABSTRACT

Successive palletized stacks of blanks in a layer of such stacks on a penetrable support of cardboard or the like are lifted off the support by a substantially horizontal plate- or blade-like implement which is caused to penetrate between the upper side of the support and the underside of a selected stack prior to lifting of the selected stack off the support for transfer onto a conveyor or into a blank converting machine, such as a cigarette packing machine. An optical or other suitable monitoring unit has one or more sensors which share the movements of the implement to detect, and to effect the generation of defect signals in response to the detection of, improper operation of the apparatus, such as the penetration of the implement through and subsequent lifting of a portion of the support with a selected stack.

BACKGROUND OF THE INVENTION

[0001] The invention relates to improvements in methods of an inapparatus for temporarily storing commodities and for removing, whennecessary, commodities from storage. More particularly, the inventionrelates to improvements in methods of and in apparatus for removing(depalletizing) commodities from temporary storage facilities in theform of pallets. Typical examples of commodities which can bemanipulated in accordance with the improved method and with or by theimproved apparatus are stacks of superimposed articles, e.g., flat orsubstantially flat blanks of paper, cardboard, plastic material and/ormetallic foil which are designed for conversion into containers orreceptacles (such as packets) for arrays of plain or filter cigarettesor other articles or products of the tobacco processing industry. Stillmore particularly, the invention relates to improvements in methods ofand in apparatus for depalletizing commodities which are temporarilydeposited on normally at least slightly deformable and/or penetrablesupports in the form of sheets, tarpaulins or panels which are placedbetween superimposed layers of commodities on pallets or analogousconveyances.

[0002] Depalletizing apparatus of the category of apparatus to which thepresent invention pertains are disclosed in European patents Nos. 0 532949 A1, 0 363 722 B2 and 0 354 873 B1. The patented apparatus aredesigned to singularize accumulations of blanks which are stacked onpallets and are to be fed to packing machines, such as cigarette packingmachines, for conversion into portions of or into entire packets, e.g.,into packets each of which is dimensioned and configurated to accept andconfine an array of twenty plain or filter cigarettes in the customaryquincunx formation.

[0003] A modern high-speed cigarette packing machine (or another blankprocessing or converting machine) is designed to turn out hugequantities of packaged products per unit of time. Thus, even arelatively short interruption of the feed of blanks to such a machinecan entail enormous losses in output. Therefore, such machines are oftencombined with a conveyor system which employs mobile pallets capable oftemporarily storing numerous stacks of superimposed blanks, preferablyin a distribution to afford convenient access to the stacks in a givensequence and unimpeded transfer into one or more blank-receivingmagazines of a packing machine.

[0004] As mentioned above, it is already known to employ pallets whichare designed to temporarily receive and transport large numbers ofstacks of superimposed blanks made of paper, cardboard and/or othermaterial or materials, often in the form of several superimposed layerswhich are separated from each other by sheet-like or analogous supportsand each of which can contain a plurality (e.g., several dozens) ofcoplanar stacks. For example, the supports between neighboringsuperimposed layers of stacks of paper or cardboard blanks can be madeof cardboard or a sheet- or panel-like material of similar consistency,and a pallet can support a substantial number of layers with supports(e.g., six cardboard panels) between neighboring layers.

[0005] Certain presently known depalletizing apparatus employ a tool orimplement which is movable in several directions so that it can becaused to penetrate between the upper side of a topmost (or the only)support and the underside of a selected stack on such topmost or onlysupport. The next step involves a lifting of the selected stack aboveand away from the upper side of the support and the transfer of the thuslifted stack onto a suitable conveyor which delivers the stacks into theblank-receiving magazine of a packing machine. As a rule, and in orderto facilitate and simplify the introduction of the implement between theupper side of a support and the underside of a selected stack on suchsupport, the implement is borne by a drive which can move the implementin the direction of the X, Y and Z axes, namely up and down (Z axis) aswell as in a horizontal plane in two directions (X and Y axes) extendingat right angles to each other. Once the implement has been moved to arequired level (at the upper side of a support), it is moved in thedirection of the X or Y axis to penetrate between the upper side of thesupport and the underside of the lowermost blank in a selected stack.

[0006] Problems arise when the upper side of a support is not smooth oris not flat or is slotted or otherwise damaged (e.g., as a result ofrepeated use) so that the normally sharp or reasonably sharp leadingedge of the implement penetrates into and thereupon lifts a portion ofthe support together with a selected stack above it. This can result inundesirable shifting of one or more neighboring stacks on the partiallylifted support and/or in at least some undesirable shifting (or completecollapse) of the stack overlying the implement. In either event, thetransfer of stacks from the pallet must be interrupted for a certaininterval of time to permit for manual separation of the implement fromthe lifted portion of the support as well as for the reestablishment oforderly distribution, orientation and configuration of neighboringstacks. This can entail huge losses in output, especially if theimpaling and lifting of a portion of a support is detected with acertain delay. In many instances, an irregularity in the depalletizingoperation can be remedied only upon stoppage of an entire productionline, e.g., a production line embodying one or more cigarette rodmakers, one or more filter tipping machines and one or more packingmachines.

OBJECTS OF THE INVENTION

[0007] An object of the invention is to provide a novel and improvedmethod of depalletizing stacks of superimposed blanks or other types ofcommodities in such a way that losses attributable to improper removalof a commodity are reduced to a minimum.

[0008] Another object of the invention is to provide a method which canbe practiced with apparatus constituting relatively minor but ingeniousdepartures from conventional depalletizing apparatus.

[0009] A further object of the invention is to provide a method which,though especially suitable for the practice in connection with themanipulation of paper, cardboard or other blanks which are to beconverted into packets or other types of receptacles or containers forsmokers' products, can be resorted to with equal or similar advantagefor the depalletizing of many other types of commodities which are to bemanipulated in a highly predictable fashion and with a minimum ofsupervision by and/or assistance from attendants.

[0010] An additional object of the invention is to provide a novel andimproved depalletizing method which can be practiced by resorting tosimple, compact and relatively inexpensive apparatus for predictableremoval of commodities from available pallets and/or supports.

[0011] Still another object of the invention is to provide a novel andimproved apparatus for the practice of the above outlined method.

[0012] A further object of the invention is to provide the apparatuswith novel and improved means for rapidly and reliably detectingirregularities in the depalletizing of stacks of blanks or other typesof commodities.

[0013] Another object of the invention is to provide a machine whichemploys one or more depalletizing apparatus exhibiting the aboveoutlined features and advantages.

[0014] An additional object of the invention is to provide a novel andimproved combination of a mobile commodity manipulating implement, meansfor moving the implement relative to commodities on a pallet, and meansfor detecting and indicating the detection of irregularities in thedepalletizing of commodities.

[0015] Still another object of the invention is to provide novel andimproved methods and apparatus for feeding accumulations of paper,cardboard or other blanks to one or more packing machines, particularlyto one or more machines for packing arrays of plain or filter cigarettesor other smokers' products.

[0016] A further object of the invention is to provide a depalletizingapparatus which requires less attention on the part of one or moreattendants than heretofore known depalletizing apparatus.

[0017] Another object of the invention is to provide an apparatus whichis constructed, assembled and adapted to be operated in such a way thatthe departures, if any, of its operation from an optimum mode ofoperation can be remedied or eliminated within shorter intervals of timethan those of conventional apparatus, such as those disclosed in theabove-enumerated European patents.

SUMMARY OF THE INVENTION

[0018] One feature of the present invention resides in the provision ofa method of removing a commodity (such as a stack of paper blanks or thelike) from the upper side of a support by means of an apparatus whichincludes a substantially horizontal lifting implement movable in aplurality of directions including downwardly toward, upwardly away fromand along the upper side of the support. The improved method comprisesthe steps of introducing the implement between the commodity and theupper side of the support, monitoring the position of at least one ofthe implement, the support and the commodity not later than uponcompletion of the introducing step and generating a signal at least whenthe monitored position departs from a predetermined position, and movingthe implement and the commodity relative to and away from the support atleast when the monitoring step does not result in the generation of asignal denoting that the monitored position departs from thepredetermined position.

[0019] As already mentioned above, the commodity can comprise at leastone stack of superimposed substantially flat blanks of paper, cardboard,plastic material, metallic foil and/or others.

[0020] The monitoring step can be carried out at least in the course ofthe introducing step or upon completion of the introducing step.

[0021] The signal which is generated in the course of the monitoringstep can constitute a defect signal, and such method can furthercomprise the step of blocking the moving step in response to thegeneration of a defect signal. Such method can further comprise the stepof correcting (e.g., manually) the monitored position in response to thegeneration of a defect signal.

[0022] The introducing step can include moving the implement downwardlyat least close to the upper side of the support adjacent the commodityto be lifted off the support, and thereupon advancing the implementalong the upper side of the support to cause the implement to enterbetween such upper side and the underside of the commodity.

[0023] The method can further comprise the step of lifting at least aportion of the implement and at least a portion of the commodity aboveand normally away from the upper side of the support subsequent to theintroducing step and prior to or simultaneously with the monitoringstep. The monitoring step preferably includes monitoring the position ofthe support. The signal can be generated when the monitoring stepreveals a lifting of at least a portion of the support with the portionsof the commodity and the implement. The aforementioned lifting step caninclude lifting or raising portions of the commodity and of theimplement through a distance in the range of several millimeters, e.g.,in the range of approximately 10 mm.

[0024] The monitoring step can include optically scanning the positionof the support. Alternatively or in addition to optical scanning, themonitoring step can include mechanically, hydraulically or pneumaticallyscanning the position of the support.

[0025] Another feature of the invention resides in the provision of anapparatus for removing commodities from the upper side of a support. Theimproved apparatus comprises a displacing unit including a substantiallyhorizontal lifting implement and means for moving the implement in aplurality of directions including downwardly toward, upwardly away fromand along the upper side of the support so that the implement can beintroduced between the upper side of the support and a selectedcommodity at such upper side, means for monitoring the position of atleast one of the implement, the support and the selected commodity notlater than upon completion of introduction of the implement between theupper side of the support and the underside of the selected commodityincluding means for generating signals denoting the monitored position,and means for evaluating such signals.

[0026] The means for generating signals can be arranged to generatedefect signals when the monitored position of the implement and/orselected commodity and/or support departs from a predetermined position,and the moving means is preferably operative to move the implement andthe selected commodity away from the upper side of the support at leastin the absence of generation of a defect signal.

[0027] In accordance with a presently preferred embodiment of theinvention, the monitoring means preferably includes means for monitoringthe position of the support. Such monitoring means can comprise aposition sensor which is carried by the moving means and extends towardthe upper side of the support. The arrangement can be such that thesignals denote the position of that portion of the support which islocated beneath the implement or beneath a portion of the implement ifthe latter is permitted or caused to penetrate into and through thesupport.

[0028] The monitoring means can include an optical sensor for theposition of the support, and such sensor is preferably borne by themoving means for the implement. The material and/or the coating of thesupport can be selected in such a way that its upper side reflectsradiation, and the optical sensor can include a source of radiation andmeans for directing radiation from such source against the upper side ofthe support. The signal generating means of such monitoring means isoperative to generate signals denoting at least one characteristic(e.g., the intensity) of radiation which is being reflected by the upperside of the support.

[0029] The moving means can include means for moving at least a portionof the implement and at least a portion of the selected commodityupwardly to predetermined positions subsequent to introduction of theimplement between the upper side of the support and the underside of theselected commodity, and the monitoring means of such apparatus cancomprise means for monitoring the position of the support in suchpredetermined positions of the portion of the implement and portion ofthe selected commodity. The signal generating means of such monitoringmeans is preferably arranged to transmit to the evaluating means asignal denoting the monitored position of the support in thepredetermined positions of the portions of the implement and theselected commodity.

[0030] The monitoring means is preferably borne by the means for movingthe implement and can include a mechanical and/or a fluid-operated(hydraulic or pneumatic) sensor which constitutes or forms part of thesignal generating means. The fluid-operated sensor can include a dynamicpressure transducer.

[0031] The novel features which are considered as characteristic of theinvention are set forth in particular in the appended claims. Theimproved apparatus itself, however, both as to its construction and itsmode of operation, together with numerous additional important andadvantageous features thereof, will be best understood upon perusal ofthe following detailed description of certain presently preferredspecific embodiments with reference to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0032]FIG. 1 is a perspective view of a pallet for temporary storage ofsuperimposed layers of commodities with the neighboring layers separatedfrom each other by sheet-like supports of cardboard or the like in amanner for depalletizing in accordance with the method and by resortingto the apparatus of the present invention;

[0033]FIG. 2 is an elevational view of an apparatus which embodies oneform of the present invention and wherein the lifting implement is heldin a position preparatory to penetration between the upper side of asupport and the underside of a selected commodity; and

[0034]FIG. 3 is a similar elevational view but showing the implement andthe selected commodity in partially lifted positions, and furthershowing a portion of the support in an improper position which thesupport assumes as a result of traversal by the relatively sharp leadingedge of the implement.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0035]FIG. 1 shows a standard pallet 1 which carries an array ofblock-shaped commodities 2, e.g., stacks of superimposed at leastsubstantially flat blanks of paper, cardboard and/or other suitablematerial. The blanks can be designed for conversion into packets forplain or filter cigarettes if the pallet 1 is utilized in a productionline to temporarily store commodities 2 (hereinafter called stacks forshort) which are to be transferred into the magazine(s) of one or morepacking machines for rod-shaped articles of the tobacco processingindustry. However, it is to be understood that the method and apparatusof the present invention can be utilized for the manipulation(depalletizing) of other types of commodities in machines or productionlines which may but need not necessarily be utilized in the tobaccoprocessing industry.

[0036] The stacks 2 are arranged in several horizontal layers, and eachsuch layer rests on a sheet- or panel-like support 3, e.g., a supportmade of cardboard or the like. The number of supports 3, the number oflayers of stacks 2, and the number of stacks 2 in each layer can departfrom those shown in FIG. 1. The manner in which the palllet 1 can beloaded with layers of stacks 2 and with supports 3 and/or the manner oftransporting the pallets to and from a depalletizing station form nopart of the present invention. The neighboring stacks 2 in thelongitudinally and/or transversely extending rows of stacks in a layermay but need not actually abut each other. FIG. 1 shows that the longersides of neighboring stacks 2 in a layer are closely adjacent oractually abut each other but the shorter sides of neighboring stacks arespaced apart from one another.

[0037] The purpose of the supports 3 is to stabilize the layers ofstacks 2 as well as to stabilize the entire (multi-layer) accumulationof stacks on the pallet 1.

[0038] One presently preferred apparatus (4) for depalletizingaccumulations of stacks 2 of the type shown in FIG. 1 is illustrated inFIG. 2. The lower part of FIG. 2 shows a portion of a single support 3(such as the topmost support on the pallet 1 of FIG. 1) and three stacks2.1, 2.2 and 2.3. The stack 2.1 can be said to constitute a selectedstack or commodity because it is about to be lifted off the upper sideof the support 3. The support 3 of FIG. 2 is removed as soon as the laststack (such as 2.1) at the upper side of this support is removed by theimproved apparatus 4. The stacks 2.2 and 2.3 (and all other stacks inthe layer including the stacks 2.2, 2.3) are then ready to bedepalletized in the same way as will be described hereinafter inconnection with the removal of the selected stack 2.1.

[0039] The apparatus 4 comprises a stack displacing unit which includesa substantially horizontal plate-like lifting implement 17 (hereinaftercalled plate for short) and means for moving the plate 17 in a pluralityof directions (indicated by the arrows X, Y and Z). The movements of theplate 17 include movements downwardly toward (arrow Z) and upwardly awayfrom the upper side of the support 3, as well as back-and-forthmovements in several (such as two) directions (arrows X and Y) in atleast substantial parallelism with the upper side of the support 3. Suchmovability of the plate 17 renders it possible to (automatically ormanually) move (arrow Z) the preferably thin (and hence relativelysharp) leading edge 18 of the plate into actual contact with or close tothe upper side of the support 3 and to thereupon move the plate 17 inthe direction of the arrow X and/or Y in order to locate the leadingedge 18 adjacent one side of the selected stack 2.1. When suchpreliminary positioning of the plate 17 is completed, the plate is readyto be moved along the upper side of the support 3 so that its leadingedge 18 is introduced between such upper side and the underside of thelowermost blank of the selected stack 2.1 (see FIG. 3).

[0040] The aforementioned means for moving the plate 17 in and counterto the directions indicated by the arrows X, Y and Z includes a carrieror head 6 which is movable up and down (arrow Z) along upright guides 7.The upright guides 7 are movable back and forth (arrow Y) alonghorizontal paths relative to a first track 8, and the track 8 is movablehorizontally (arrow X) along a further or second track (not shown),namely along a path which is or can be exactly normal to the horizontalpaths for the upright guides 7 along the first track 8. Thus, theleading edge 18 of the plate 17 can be moved downwardly toward andupwardly away from the upper side of the support 3 of FIGS. 2 and 3 bycausing the carrier 6 to move along the upright guides 7, and theleading edge 18 can also be moved along the upper side of the support 3by moving the guides 7 relative to the track 8 and/or by moving theguides 7 and the track 8 relative to the non-illustrated second track.The means for moving the carrier 6 relative to the guides 7, the guides7 relative to the first track 8, and the track 8 relative to the secondtrack can comprise fluid-operated motors, electric motors or any othersuitable prime movers the exact design of which forms no part of thepresent invention. All that counts is to provide the displacing unit ofthe apparatus 4 with moving means which can advance the plate 17downwardly toward and upwardly away from the upper side of the support 3as well as along the upper side of the support 3 so that the leadingedge 18 (and thereupon an additional (e.g., major) part of the plate)can be introduced between the support 3 and the underside of thelowermost blank in the selected stack 2.1.

[0041] The displacing unit of the apparatus 4 can be provided with oneor more sensors which track the movements of the plate 17 relative tothe upper side of the support 3 and transmit appropriate signals to anevaluating circuit 31 of the apparatus 4. For example, a position sensorcan be provided to generate signals denoting the exact or approximateposition of the carrier 6 relative to the upright guides 7, i.e., toindicate the level of the leading edge 18 of the plate 17 relative tothe upper side of the support 3. Such signals can be utilized todecelerate the prime mover for the carrier 6 when the leading edge 18has been moved to a level close to the desired or optimum level relativeto the upper side of the support 3.

[0042] The carrier 6 movably or fixedly supports a substantiallyhorizontal guide 12 for one or more reciprocable rod-like guides 13 thefree end portion(s) of which carries or carry an upright guide 14vertically movably mounting the trailing portion of the plate 17. Suchtrailing portion of the plate 17 is secured to a holder 16, e.g., by oneor more threaded fasteners. As can be seen in FIGS. 2 and 3, the plate17 (which resembles or can resemble a flat tongue with a sharp edge 18)can slope downwardly through a relatively small acute angle in adirection from the holder 16 toward the upper side of the support 3.This renders it possible to move the leading edge 18 into actual contactwith the upper side of the support 3 adjacent one side of the selectedstack 2.1 while the major part of the underside of the plate 18 remainsspaced apart from the upper side of such support. Reference may be hadto the aforementioned European patent No. 0 532 943 A1 which describesand shows a plate suitable for use in the apparatus 4 of the presentinvention.

[0043] The holder 16 can be said to constitute an extension of thecarrier 6 and serves to ensure a highly accurate selection of the levelof the leading edge 18 of the plate 17 relative to the upper side of thesupport 3 before the plate 17 is caused to move along the upper side ofthe support from the position of FIG. 2 to that which is shown in FIG.3. The vertical guide 14 at the free end(s) of the vertical guide(s) 13carries a suitable prime mover (not specifically shown) which can movethe holder 16 and the plate 17 up and down for the aforementionedpurpose of selecting the exact level of the leading edge 18 with a veryhigh degree of accuracy.

[0044] A sensor 9 is provided on the holder 16 to transmit (to theevaluating circuit 31) signals denoting the exact level of the holder 16and plate 17 relative to the guide 14. A further sensor 11 is providedto transmit signals denoting the exact position of the guide 14, holder16 and plate 17 in the longitudinal direction of the guide(s) 13, i.e.,in or counter to the direction indicated by the arrow Y. Additionalsensor or sensors are or can be provided to generate and to transmit tothe evaluating circuit 31 additional signals denoting the exact positionof the plate 17 as seen in and/or counter to the direction indicated bythe arrow X and/or Y and/or Z. All this contributes to a more accuratepositioning of the leading edge 18 relative to the upper side of thesupport 3 and/or relative to the selected stack 2.1. The evaluatingcircuit 31 is or can be designed to control or regulate the operation ofvarious prime movers for the carrier 6, for the first track 8, for thesecond track, and for the holder 16.

[0045] The guide 12 and the guide(s) 13 can include or constitute one ormore fluid-operated (hydraulic or pneumatic) motors (e.g., one or moredouble-acting cylinder and piston units) which can move the guide 14toward and away from the carrier 6 in response to actuation (by theevaluating circuit 31) of one or more valves serving to regulate theflow of a fluid medium into and from the cylinder chamber or chambers ofsuch motor(s). Analogously, the guide 14 can include or constitute afluid-operated motor which can move the holder 16 (or directly the plate17) to a desired level relative to the upper side of the support 3.

[0046] It is also possible to employ an electric motor (not shown) inorder to shift the guides 13, 14 relative to the guide 12 on the carrier6. Such prime mover can further enhance the accuracy of adjustment ofthe position of the leading edge 18 of the plate 17 relative to theselected stack 2.1.

[0047] In order to facilitate the introduction of the leading edge 18 ofthe plate 17 between the upper side of the support 3 and the undersideof the lowermost blank of the selected stack 2.1, i.e., a movement ofthe plate 17 from the position of FIG. 2 to the position of FIG. 3, thecarrier 6 supports at least one but preferably two hold-down devices 19(only one shown) which flank the plate 17 at the leading edge 18 and canbe caused to bear against the upper side of the support 3 at least whenthe leading edge 18 reaches the position of readiness for advancementbeneath the lowermost blank of the selected stack 2.1. The constructionand the mode of operation or manipulation of the carrier 6 and of thehold-down device or devices 19 can be the same as described in theaforementioned European patent No. 0 532 949 A1 to which reference maybe had if necessary.

[0048] A further hold-down device 21 which is supported by the carrier 6serves to prevent deformation of the selected stack 2.1 during liftingof such stack by the plate 17. The hold-down device 21 is movable up anddown by a suitable drive 22 which is also mounted on and thus shares themovements of the carrier 6. When the selected stack 2.1 is enngaged frombelow by the upper side of the plate 17, the upper side of the topmostblank of such stack is engaged by the hold-down device 21 so that theconfiguration of the stack 2.1 remains at least substantially unchangedduring subsequent lifting above and movement away from the support 3,e.g., for the purpose of depositing the stack 2.1 in or on a suitableconveyor for delivery to a packing machine or for introduction of thestack 2.1 directly into the blank-receiving magazine of a packingmachine.

[0049] The carrier 6 further supports a blank removing device 23 havingat its lower end at least one suction cup 24 or another suitable blankattracting or lifting component which is put to use, when necessary, toremove from the upper side of the support 3 one or more blanks whichremained on the support subsequent to removal of all stacks or aparticular stack (such as 2.1). For example, and assuming that theleading edge 18 of the plate 17 failed to penetrate between the upperside of the support 3 and the underside of the lowermost blank of theselected stack 2.1 shown in FIGS. 2 and 3, the blank or blanks whichremained on the support 3 upon removal (depalletizing) of the majorportion of the stack 2.1 can be gathered and removed by the suction head24. The upper portion of the blank removing device 23 can include orconstitute a prime mover (e.g., a fluid-operated motor) which can changethe level of the suction cup 24 relative to the carrier 6. Suchmovability of the suction cup 24 relative to the carrier 6, combinedwith the movability of the carrier in and counter to the directionsindicated by the arrows X, Y and Z, suffices to ensure that the suctioncup 24 can reach and remove blanks on any given portion of the upperside of the support 3.

[0050] In addition to its just described function of gathering discreteblanks off the upper side of the support 3, the device 23 can performthe function of assisting or replacing the hold-down device 21, i.e., ofcausing the suction cup 24 to bear upon the upper side of the topmostblank of a stack (such as 2.1) which is to be removed from the support3. The arrangement can be such that, as a rule, the suction head 24 isused as a hold-down device; however, if one or more blanks happen toremain on a support upon depalletizing of a complete layer of stacks, orupon removal of a particular stack, the device 23 can be put to use as ameans for gathering and removing such stray blank or blanks. This mightbe desirable for several reasons, i.e., to prevent a loose blank frominterferring with the advancement of the leading edge 18 of the plate 17along the upper side of a support 3 to a desired (optimum) positionand/or to ensure that a support which has been relieved of therespective layer of stacks can be readily removed and immediately put torenewed use in conjunction with the same pallet or with another pallet.

[0051] In accordance with an important feature of the invention, theapparatus 4 further comprises a unit 26 which serves as a means formonitoring the position of the plate 17, of a selected stack (such as2.1) and/or of the support 3 not later than when the step of introducingthe leading edge 18 of the plate 17 between the upper side of thesupport 3 and the underside of the selected stack is completed. Themonitoring unit 26 comprises means 29 for generating signals whichdenote the monitored position of the plate 17, selected stack and/orsupport 3 and for transmitting such signals to the evaluating circuit31. The purpose of the monitoring unit 26 and of its signal generatingmeans 29 is to generate defect signals when the actual introduction ofthe plate 17 between the upper side of the support 3 and the undersideof a selected stack (2.1) departs from a desirable or optimumintroduction.

[0052] For example, and as shown in FIG. 3, the just completedintroduction of the leading edge 18 of the plate 17 beneath the stack2.1 was unsatisfactory because the leading edge 18 has been caused topenetrate through the adjacent portion of the support 3 and the latteractually overlies such leading edge. In other words, the leading edge 18is located at the underside, in lieu of at the upper side, of thesupport 3.

[0053] The monitoring unit 26 is designed to monitor the position ofthat portion of the support 3 which is adjacent the plate 17 when theaforediscussed introducing step is completed. To this end, the unit 26comprises an optical position sensor including a source of radiation 32(such as light). The source includes or is adjacent the upper end of alight conductor 28 having a radiation discharging/receiving end 27serving to direct at least one beam of radiation 32 toward the upperside of (e.g., through a window in) the plate 17. The radiation which isreflected back into the conductor 28 is transmitted to the signalgenerating means 29 which generates a defect signal (under thecircumstances prevailing in FIG. 3) or a signal denoting that theplate-introducing step has been completed in a satisfactory manner,i.e., that the partially lifted selected stack can be moved off and awayfrom the upper side of the support 3 to be delivered to a conveyor orinto a magazine for blanks.

[0054] The actual radiation source can be installed in or can form partof the signal generating means 29. Thus, a beam of radiation 32 canissue from the source of the signal generating means 29 to be propagatedin the conductor 28, to issue at the end 27, to be reflected by thesupport 3 back into the end 27, and to be propagated in the conductor 28back to the signal generating means 29 which generates a signal denotingthe position (level) of that portion of the support 3 which is adjacentthe plate 17. The manner in which a signal generating means (29) canemit radiation and can be provided with a suitable transducer for thegeneration and transmission (to the evaluating circuit 31) of signalswhich are indicative of the monitoring of the position of the support 3at the plate 17 is well known to those skilled in the relevant arts.

[0055] As already mentioned above, the evaluating circuit 31 receivesand processes several additional signals including those transmitted bythe sensors 9 and 11 (as well as by one or more additional sensors, ifany). The evaluating circuit 31 is shown as a discrete component part ofthe apparatus 4; however, it is often preferred to integrate theevaluating circuit 31 into the control circuitry of the machine orproduction line in which or in conjunction with which the apparatus 4 isbeing put to use.

[0056] The operation of the apparatus 4 is as follows:

[0057] It is assumed that the apparatus is to lift the selected stack2.1 of FIG. 2 off the upper side of the support 3. The first stepinvolves the positioning of the carrier 6 relative to the upright guides(arrow Z), the guides 7 relative to the first track 8 (arrow Y) and thefirst track 8 relative to the second track (arrow X), as well as theholder 16 (by way of the parts 12, 13, 14) relative to the carrier 6 andholder 14, in such a way that the leading edge 18 of the plate 17assumes a desired position relative to the selected stack 2.1 Thus, andas shown in FIG. 2, the leading edge 18 is closely adjacent the upperside of the support 3 at a locus closely or immediately adjacent thenearest edge of the lowermost blank of the stack 2.1. The hold-downdevices 19 are operative, i.e., they are caused to depress the adjacentportions of the support 3 so that the leading edge 18 is even morelikely to penetrate between the upper side of the support 3 and theunderside of the lowermost blank forming part of the selected stack 2.1.

[0058] Alternatively, the leading edge 18 of the plate 17 can be movedto the position of FIG. 2 in two successive stages. The first stage caninvolve a coarse adjustment by the carrier 6 (arrows X, Y, Z) and holder16 (via guides 12, 13, 14) so that the leading edge 18 is moved to aposition reasonably close to the desired or optimum position forpenetration between the support 3 and the stack 2.1. The next-followingsecond stage involves a precision or final adjustment of the position ofthe leading edge 18, e.g., with assistance from one or more sensors (notshown) at or close to the hold-down devices 19. Such sensor or sensorscan generate signals which are evaluated by the circuit 31 and areutilized to effect final adjustments of the leading edge 18 (i.e., ofthe plate 17) in the directions of the arrows X and Y. Moreover, asignal from the sensor 9 can be utilized to thereupon move the holder 16and the plate 17 relative to the guide 14 (arrow Z) so that the leadingedge 18 is immediately adjacent or actually contacts the upper side ofthe support 3 at the hold-down devices 19.

[0059] The movement of the holder 16 and plate 17 relative to the guide14 is terminated when the signal from the sensor 9 to the evaluatingcircuit 31 indicates that the leading edge 18 is located at an optimumlevel relative to the upper side of the support 3. That position of theleading edge 18 which is shown in FIG. 2 is presumed to be an optimumposition, i.e., a position which is least likely to cause any problemsin the course of the next-following steps which normally involve theintroduction of an adequate portion of the plate 17 between the support3 and the stack 2.1, lifting of the plate 17 and of the stack 2.1 aboveand away from the support 3, and the transfer of the stack 2.1 from theplate 17 onto a conveyor, into a magazine or to another destination.

[0060] The movement of the plate 17 from the position of FIG. 2 to theposition of FIG. 3 is effected by moving the guides 13 and 14 (with theholder 16) relative to the guide 12 and/or by moving the upright guides7 along the first track 8. Thus, the movement of the plate 17 from theposition of FIG. 2 to the position of FIG. 3 takes place along ahorizontal path defined by the guide(s) 13. If the leading edge 18encounters an obstruction, such as an upwardly projecting portion of thesupport 3, the plate 17 penetrates into and through the relatively thinsupport in a manner as shown in FIG. 3 so that the leading edge 18 islocated beneath (rather than at a level above) the adjacent portion ofthe support. For example, a portion of the support 3 beneath theselected stack 2.1 (above the stack 2.3) can be caused to bulge upwardlyas a result of the action of the hold-down devices 19 in combinationwith frictional engagement between the leading edge 18 and the upperside of the support 3. The leading edge 18 is caused to cut an elongatedslot in the support 3 on its way to the position which is shown in FIG.3.

[0061] If the undesirable penetration of the plate 17 through thesupport 3 is not detected in time, i.e., if the plate 17 is thereuponcaused to move upwardly in order to advance the stack 2.1 above and awayfrom the stack 2.3, the plate 17 lifts and ultimately tears up thatportion of the support which overlies the plate. If the stack 2.1 is notthe last stack of the layer of, for example, thirtyfive stacks (seeFIG. 1) on the support 3 of FIG. 3, at least some of the stacks adjacentthe stack 2.1 are overturned, partially overturned or otherwise affectedso that they are no longer in conditions for predictable depalletizing.Each such occurrence necessitates a lengthy interruption of thedepalletizing operation in order to enable one or more attendants toremove all affected stacks before the plate 17 can be caused to resumethe removal of remaining stacks off the pierced support 3 or off thenext-following (lower) support.

[0062] In order to ensure timely detection of a less than satisfactoryoperation of the apparatus 4, each depalletizing operation preferablyincludes the additional step which is shown in FIG. 3. Thus, prior toactually removing a stack (2.1) which at least partially overlies theplate 17, the latter is moved upwardly through a predetermined distance(e.g., in the range of one or more millimeters, preferably about 10 mm)to lift the stack 2.1 and to enable the monitoring unit 26 to even morereliably and accurately ascertain whether or not the monitored part ofthe support 3 at the plate 17 is in a position which is indicative ofsatisfactory lifting of the stack 2.1 above and away from the support.The plate 17 can be lifted by the carrier 6 which is caused to moveupwardly (counter to the direction indicated by the arrow Z) along theupright guides 7 and thus lifts the plate 17 by way of the guides 12,13, 14 and holder 16.

[0063] The monitoring unit 26 is caused to ascertain the position (andhence the condition) of the support 3 at the plate 17 as soon as theupward movement of the plate 17 through the distance of a fewmillimeters is completed. The beam of radiation 32 issuing from thesignal generating means 29 passes through the plate 17 (e.g., via theaforementioned window in the plate) and is reflected by the raisedportion of the support 3 beneath the plate 17. The thus reflectedradiation causes the signal generating means 29 to generate a defectsignal which is displayed or is rendered audible or is otherwiseprocessed, e.g., by the evaluating circuit 31. A signal which isgenerated at 29 when the leading edge 18 did not penetrate through thesupport 3 in a manner as shown in FIG. 3 is sufficiently different froma defect signal to permit unimpeded continuation of the depalletizingoperation.

[0064] The arrangement is preferably such that, if the signal generatingmeans 29 transmits to the evaluating circuit 31 a defect signal, thecircuit 31 prevents any further movements of the plate 17 and of thestack (2.1) thereon until the cause of malfunction (irregularity in thedepalletizing operation) is detected and eliminated. In fact, a defectsignal which is furnished by the signal generating means 29 and isprocessed by the evaluating circuit 31 can be utilized to effect atemporary stoppage of the machine or production line which receivesstacks of blanks from the plate 17.

[0065]FIG. 3 illustrates only one of defective operations which can bedetected by the monitoring unit 26 or an equivalent monitoring unit.Penetration of the leading edge 18 of the plate 17 into a support 3 ofcardboard or the like has been illustrated in FIG. 3 because it is oneof more frequent causes of malfunctioning of the depalletizing apparatus4. The aforedescribed lifting of the plate 17 through a short distanceprior to actual evacuation of the stack overlying the plate 17constitutes an optional but highly desirable feature because itcontributes to the reliability of detection of defective operation ofthe apparatus 4 and/or of flaws in a support 3 and/or of excessiveresistance of the lowermost blank of a stack to separation from theupper side of the support below it so that the plate 17 is compelled todamage or further damage or displace the support during advancement ofthe leading edge 18 from the position of FIG. 2 to that shown in FIG. 3.

[0066] The improved apparatus is susceptible of numerous additionalmodifications. For example, at least the conductor 28 of the opticaldetector forming part of the monitoring unit 26 can be mounted on one ofthe hold-down devices 19 or on the plate 17 or on the carrier 6. Infact, the signal generating means 29 can be mounted on one of thehold-down devices 19 or on the plate 17 or on the carrier 6 so that theconductor 28 can be dispensed with.

[0067] Furthermore, an optical monitoring unit 26 can be utilized incombination with or it can be replaced by a suitable mechanical orfluid-operated (pneumatic or hydraulic) monitoring unit. All that countsis to provide the apparatus 4 with a suitable monitoring unit capable ofgenerating defect signals when a depalletizing operation is not beingcarried out in a prescribed or acceptable manner, e.g., when the leadingedge 18 of the plate (implement) 17 has penetrated into the adjacentportion of a support.

[0068] The generation of a defect signal can be utilized to alert one ormore attendants or to initiate an automatic remedial action, e.g., thetransfer of one or more stacks into a collecting receptacle for wastematerial before the normal depalletizing operation is resumed.

[0069] In lieu of or in addition to monitoring of the support 3, theapparatus 4 can be equipped with means for monitoring the dimensions,the shape, the weight and/or other parameters or characteristics ofsuccessive stacks in order to ascertain whether or not the stacks areready to be transported into a packing or other blank processingmachine.

[0070] As concerns the various types of monitoring units which can beutilized in the apparatus of the present invention, reference may be hadto any one of numerous available publications dealing with pneumatic,hydraulic, mechanical, optical and other sensors. For example, the partof the article by S. L. Sorsen on pages 77 and 79 in the May 1964 issueof the publication entitled “Control Engineering” describes andillustrates various modes of monitoring the quality, speed, position andheight difference of sheets made of paper, steel, plastics and/ortextile materials. The illustrations show the basic components (limitswitches) of mechanical monitoring means, of light- or air-operatedpresence detectors, as well as of various proportional sensors. It isbelieved that a pneumatic proximity proportional sensor of the typeshown and described at 10 on page 79 of the article by Sorsen isparticularly suitable for use with or in lieu of the monitoring unit 26shown in FIGS. 2-3. Such monitoring units, as well as numerous updatedversions thereof, can be utilized with or as substitutes for themonitoring unit 26 of FIGS. 2-3 without departing from the spirit of theinvention.

[0071] An advantage of the apparatus 4 which is shown in FIGS. 2 and 3is that a defective depalletizing operation can be detected (and thenecessary remedial steps undertaken) before a defective stack or adefect in the support affects the condition of other stacks on the samesupport.

[0072] Another important advantage of the improved method and apparatusis that a defective depalletizing operation can be detected immediatelyafter occurrence so that a remedial action can be undertaken before thestart of a chain reaction, i.e., of a series of two or moreunsatisfactory depalletizing operations. This shortens the intervals ofidleness of the blank processing machine and reduces the numbers ofblanks or stacks of blanks which are damaged or otherwise affected as aresult of a defective depalletizing operation. Thus, even a ratherserious malfunction, such as that shown in FIG. 3, does not or need notcause substantial losses in output and/or damage to a large number ofblanks.

[0073] Without further analysis, the foregoing will so fully reveal thegist of the present invention that others can, by applying currentknowledge, readily adapt it for various applications without omittingfeatures that, from the standpoint of prior art, fairly constituteessential characteristics of the generic and specific aspects of theabove outlined contribution to the art of depalletizing commodities and,therefore, such adaptations should and are intended to be comprehendedwithin the meaning and range of equivalence of the appended claims.

What is claimed is:
 1. A method of removing a commodity from an upper side of a support by means of an apparatus which includes a substantially horizontal lifting implement movable in a plurality of directions including downwardly toward, upwardly away from and along the upper side of the support, comprising the steps of introducing the implement between the commodity and the upper side of the support; monitoring the position of at least one of the implement, the support and the commodity not later than upon completion of said introducing step and generating a signal at least when the monitored position departs from a predetermined position; and moving the implement and the commodity relative to and away from the support at least when the monitoring step does not result in the generation of a signal denoting that the monitored position departs from the predetermined position.
 2. The method of claim 1, wherein the commodity comprises at least one stack of superimposed substantially flat blanks.
 3. The method of claim 1, wherein said monitoring step is carried out at least in the course of said introducing step.
 4. The method of claim 1, wherein said monitoring step is carried out upon completion of said introducing step.
 5. The method of claim 1, wherein said signal is a defect signal, and further comprising the step of blocking said moving step in response to the generation of a defect signal.
 6. The method of claim 5, further comprising the step of correcting the monitored position in response to the generation of a defect signal.
 7. The method of claim 1, wherein said introducing step includes moving the implement dowardly at least close to the upper side of the support adjacent the commodity and thereupon advancing the implement along the upper side between the commodity and the upper side of the support.
 8. The method of claim 1, further comprising the step of lifting at least a portion of the implement and of the commodity above and normally away from the upper side of the support subsequent to said introducing step and prior to said monitoring step.
 9. The method of claim 8, wherein said monitoring step includes monitoring the position of the support.
 10. The method of claim 9, wherein said signal is generated when said monitoring step reveals a lifting of at least a portion of the support with said portions of the commodity and the implement.
 11. The method of claim 9, wherein said lifting step includes lifting portions of the commoditiy and of the implement through a distance in the range of approximately 10 mm.
 12. The method of claim 9, wherein said monitoring step includes optically scanning the position of the support.
 13. The method of claim 9, wherein said monitoring step includes mechanically scanning the position of the support.
 14. The method of claim 9, wherein said monitoring step includes the utilization of a fluid-operated monitoring device.
 15. Apparatus for removing commodities from an upper side of a support, comprising a displacing unit including a substantially horizontal lifting implement and means for moving said implement in a plurality of directions including downwardly toward, upwardly away from and along the upper side of the support so that the implement can be introduced between the upper side of the support and a selected commodity at the upper side; means for monitoring the position of at least one of said implement, the support and the selected commodity not later than upon completion of introduction of the implement between the upper side of the support and the selected commodity, including means for generating signals denoting the monitored position; and means for evaluating said signals.
 16. The apparatus of claim 15, wherein said generating means is arranged to generate defect signals when the monitored position departs from a predetermined position, said moving means being operative to move said implement and the selected commodity away from the upper side of the support at least in the absence of generation of a defect signal.
 17. The apparatus of claim 15, wherein said monitoring means includes means for monitoring the position of the support.
 18. The apparatus of claim 17, wherein said monitoring means comprises a position sensor carried by said moving means and extending toward the upper side of the support.
 19. The apparatus of claim 18, wherein said signals denote the position of the support beneath said implement.
 20. The apparatus of claim 15, wherein said monitoring means includes an optical sensor for the position of the support, said sensor being borne by said moving means.
 21. The apparatus of claim 20, wherein the upper side of the support reflects radiation and said sensor includes a source of radiation and means for directing radiation from said source against the upper side of the support, said signal generating means being operative to generate signals denoting the characteristics of radiation being reflected by the upper side of the support.
 22. The apparatus of claim 15, wherein said moving means includes means for moving at least a portion of said implement and at least a portion of the selected commodity upwardly to predetermined positions upon introduction of said implement between the upper side of the support and the selected commodity, said monitoring means including means for monitoring the position of the support in said predetermined positions of said portion of said implement and said portion of the selected commodity and said signal generating means being arranged to transmit to said evaluating means a signal denoting the monitored position of the support in said predetermined positions of said portions of said implement and the selected commmodity.
 23. The apparatus of claim 15, wherein said monitoring means is borne by said moving means and includes a mechanical sensor constituting said signal generating means.
 24. The apparatus of claim 15, wherein said monitoring means is borne by said moving means and includes a fluid operated sensor constituting said signal generating means.
 25. The apparatus of claim 24, wherein said sensor is a pneumatic sensor.
 26. The apparatus of claim 24, wherein said sensor includes a dynamic pressure transducer. 